The second installment from Vocaloid 2, Kagamine Rin and Kagamine Len are 2 voice synthesizers packaged into one. According to their official blog, Rin and Len are not siblings, but mirrors of one another. In fact, the family name is comprised of "kagami" meaning "mirror" and "ne" meaning "sound". Rin and Len is also a pun for Left and Right.
Kipi makes an awesome Rin. I wonder who'd be a fitting Len for her?